Typical tape data storage and retrieval methods involve recording or writing data in tracks running length-wise down the tape, as well as retrieving or reading such data tracks from the tape. A multiple stripe head may be used to write and/or read many parallel tracks. Magnetic read/write systems may simultaneously read or write 96 tracks or more, with the ability to jog along the width of a magnetic tape to write and/or read more tracks. Optical tape data storage and retrieval systems using laser heads may operate in a similar fashion.
Magnetic and optical tape media are frequently used for long-term storage of large quantities of data, such as in data backup or archive operations. However, multiple stripe head designs become inefficient as tape length is increased for greater capacity because of the increased time it takes to access the data stored at the end of the tape. Shorter tape lengths result in quicker access time than longer tape lengths, but also result in more limited data storage capacity. A wide tape to boost capacity requires many more transducers in the head. Data throughput is also a factor of tape width and the number of heads. Limits to multiple stripe head designs include the number of heads and overall tape width.
An improved data storage method involves the use of a rotary head where the tracks are written in width-wise arcs across the tape, such as the system disclosed in U.S. Pat. No. 8,225,339, for example. Such a method results in more tape surface area available for reading/writing data by the heads. It also permits the use of wider tapes to increase storage capacity with fewer heads than would be required using traditional stripe heads.
However, this method uses only 50% or less of the duty cycle of the rotating lasers. The lasers can access the tape for one half of the head rotation, but cannot write to the tape during the rest of the rotation without overwriting previously recorded tracks. This causes unnecessary wear and tear due to the unused portion of the duty cycle, and also limits the read/write speed of the system.